【作者】 蔺绍江；

【导师】 熊惟皓；

【作者基本信息】 华中科技大学 ， 材料学， 2012， 博士

【摘要】 TiC/316L不锈钢复合材料综合了TiC颗粒的低密度、高硬度和高耐磨性的优点,同时保留了不锈钢基体高的强韧性和优良的抗蚀性能,因而在机械、化工、石油、海洋等工业领域有着巨大的应用潜力。与其他制备方法相比,粉末冶金法具有成分比例准确、处理温度低、生产效率高等优点,因而被认为是最适合颗粒增强不锈钢复合材料的制备方法。但对于采用粉末冶金法制备的复合材料而言,其产品孔隙率较高,致密化程度不够,因而,如何提高粉末冶金材料的致密化程度成为研究者十分关心的问题。为此,本文对采用粉末冶金法制备的TiC/316L不锈钢复合材料的致密化和性能展开研究,为提高粉末冶金法制备不锈钢复合材料的致密化程度,探讨了粉末冶金TiC/316L不锈钢复合材料新的致密化工艺和方法。实验采用扫描电子显微镜观察了在不同球磨方式下获得的TiC/316L复合粉末的微观形貌,并依据黄培云双对数方程和相关烧结模型分别对该粉末的压制特性及烧结行为进行了研究和分析。结果表明,采用先干磨再湿磨的球磨方式得到的复合粉末具有粒度小、混合均匀的特点,并且该粉末活性大、烧结激活能低,有利于后续的压制成形和烧结致密化。为了探讨粉末冶金TiC/316L不锈钢复合材料致密化的影响因素,研究了常规压制和温压成形对复合粉末致密化的影响,结果表明温压工艺可以提高TiC/316L复合粉末的塑性变形能力,促进压制过程中粉末颗粒的重排,从而实现压坯的致密化。在此基础上提出采用温压成形和微波烧结的复合方法制备TiC/316L不锈钢复合材料,实验结果表明,与常规粉末冶金法相比,采用该复合方法可以获得较高相对密度的复合材料试样,并且TiC颗粒分布更为均匀,减少了增强体颗粒在基体中的聚集。采用ANSYS软件模拟了增强体颗粒形状不同的复合材料的应力应变行为,结果表明,与正方形、六边形颗粒相比,采用圆形增强体颗粒,有利于复合材料应力应变的均匀分布,圆形颗粒表现出较好的强化效果。论文考察了TiC/316L不锈钢复合材料拉伸力学性能、耐磨性能和高温氧化行为的影响因素,研究发现：TiC颗粒的引入,能有效提高复合材料的抗拉强度、耐磨性能和抗氧化性能；增加压制过程中的压制压力也可以在一定程度上提高夏合材料的抗拉强度和耐磨性能。结果显示,添加10wt.%TiC的复合材料抗拉强度最高、抗氧化性能最好,添加5wt.%TiC的复合材料的耐磨性能最好；压制压力为500MPa时,复合材料具有良好的拉伸性能,压制压力为400MPa时,复合材料的耐磨性能较好。对TiC/316L不锈钢复合材料的摩擦磨损行为研究表明,提高复合材料的致密化程度和TiC颗粒在基体中的分散性,可以促进TiC颗粒在摩擦磨损过程中有效承载,阻止磨损变形,减少体积磨损量。与采用常规粉末冶金法相比,采用温压成形和微波烧结制备的复合材料因致密化程度的提高,其硬度较高,耐磨性较好。对复合材料的高温氧化行为研究表明,采用温压成形和微波烧结的复合方法获得的复合材料因为改善了TiC增强体颗粒在基体中的分布,促进了材料的致密化,较明显的降低了材料的氧化速率论文还研究了Mo添加对TiC/316L不锈钢复合材料致密化和性能的影响,研究显示,Mo的添加可以促进TiC/316L不锈钢复合材料的烧结致密化,从而有利于TiC/316L复合材料抗拉强度和耐磨性能的提高,同时,添加Mo叮以改善TiC/316L不锈钢复合材料在3.5wt.%NaCl溶液中的抗点蚀能力,也有助于降低复合材料在15wt.%H2SO4溶液中的腐蚀速率。更多还原

【Abstract】 TiC is responsible for the hardness and abrasive resistance increase while 316L stainless steel ensures the toughness and better corrosion resistance. Such combination of properties make the TiC/316L stainless steel composites very attractive for numerous applications like in mechanical, chemical, petroleum and oceanic fields. Compared with other preparation methods, powder metallurgy (P/M) is thought to be a more suitable preparation technique for particles reinforced stainless steel composites because it has many advantages, such as accurate component proportion, lower process temperature, and higher production efficiency. However, P/M materials have relatively high porosity and low densification. Thus, how to improve the densification of P/M materials is the problem that is concerned by the researchers. Therefore, this thesis researches on the densification and properties of TiC/316L stainless steel composites obtained by P/M technology. In order to improve the densification of P/M stainless steel composites, new densification methods were also investigated.In this study, microstructure characteristics of the TiC/316L composite powders obtained through different ball-milling modes were performed by means of scanning electron microscopy (SEM). Huang Pei-yun’s log-log powder compacting theory and relevant sintering theory were used to analyze the compactability and sintering behavior of those powders, respectively. The results indicated that TiC/316L composite powders prepared by the ball-milling mode of dry ball milling and then wet grinding exhibited a more small grain size, lower activation energy of sintering, and it has a beneficial effect on their subsequent compression and sintering.In order to discuss the P/M composites densification factors, a study on effect of conventional compaction and warm compaction on densification of composite powder was performed. The analysis show that warm compaction process results in the increased the plastic deformation capability of TiC/316L composite powder, which had helped to improve the particle rearrangement. As a result, the densification increases. And based on this, a new densification method for TiC/316L composites by using warm compaction and microwave sintering (WM) is put forward. It is found that the composites prepared by WM not only has high relative density, but also better distributing of TiC particles in matrix, and diminishing agglomeration of the particles than the composites prepared by conventional P/M.The effects of reinforcement particles of different shapes on the stress and strain behaviors of composites were investigated by using the ANSYS software. The simulation results indicated that the composites in which the particles are assumed all in round shape produce a better strengthening for its more uniform dispersions of stress and strain, as compared with the composites which adopt the hexagon or square particles.The factors affecting the tensile properties, abrasion resistance and high temperature oxidation behavior of TiC/316L composites were analyzed in this paper. The results show that the addition of TiC is effective in improving the tensile properties, abrasion resistance and high temperature oxidation resistance of the composites. Furthermore, the tensile strength and abrasion resistance of TiC/316L composites were increased with the increase of the pressing pressure. The experimental results demonstrate that the composites with 10wt.%TiC addition exhibited a higher tensile strength and better oxidation resistance; 5wt.% TiC/316Lcomposites exhibited a better abrasion resistance. The tensile property of the composites is better under the pressure of 500MPa than other case. A better abrasion resistance property was obtained when the pressure was 400MPa.Research on the friction and wear behavior of TiC/316Lcomposites suggests that improving the densification of composites and dispersion of TiC particles in matrix can effectively promote the loading of TiC particles during wear sliding, resist the wear deformation, and reduce volume loss of composites. The sample prepared by warm compaction and microwave sintering exhibited significantly superior densification, higher hardness and better abrasion resistance when compared with conventionally processed counterpart. Research on the high temperature oxidation behavior of TiC/316L composites show that the composites obtained by MW because of the improving of TiC particles dispersion, and thereby increment of the densification, which causes a decrease in oxidation rate.The thesis also discusses the effect of Mo content on the densification and properties of TiC/316L composites. Results show that Mo addition contributes to enhancing the densification of the composites during sintering and thus to promoting the tensile strength and abrasion resistance of the composites. Moreover, the addition of Mo is beneficial to improve the resistance to pitting in 3.5wt.%NaCl solution, and the corrosion rate of composites could appreciably decrease.更多还原